JPH0223752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure control valve that changes a set pressure by hydraulic pressure in a pilot circuit.

Conventionally, this type of pressure control valve is shown in Fig.
55-78802).

FIG. 1 shows a hydraulic circuit for driving a swivel base of a hydraulic crane. This hydraulic circuit includes a hydraulic pump 1, a pilot-operated directional valve 2
The configuration is such that the hydraulic motor 4 is connected via the. Hydraulic motor 4 drives swivel base 5 . Main circuits 6a and 6b connecting the hydraulic motor 4 and the directional control valve 2
Brake circuits 8a, 8b with pressure control valves 7a, 7b are provided between them.

The directional switching valve 2 has a neutral position 2a and switching positions 2b, 2c, and a pilot circuit 9.
It is provided with pilot parts 2d, 2e to which a, 9b are connected, and springs 2f, 2g for returning to the neutral position 2a. When the directional control valve 2 is in the neutral position 2a (when no pilot oil pressure acts on either the pilot circuits 9a or 9b), the discharge side of the hydraulic pump 1 is connected to the tank, and the main circuits 6a,
6b is closed. When located at the switching position 2b (when the pilot oil pressure acts on the pilot circuit 9a and the directional control valve 2 is operated to the switching position 2b), the hydraulic pump 1 is connected to the main circuit 6a, and the main circuit 6b is connected to the tank. Connect to. In addition, the hydraulic pump 1 is connected to the main circuit 6b at the switching position 2c (when the pilot oil pressure acts on the pilot circuit 9b and the directional control valve 2 is operated to the switching position 2c).
The main circuit 6a is connected to the tank.

Pressure control valve 7a (as pressure control valve 7b also has the same structure, only pressure control valve 7a will be explained,
The pressure control valve 7b will be explained as necessary. The pressure control valve 7b has the same parts as the pressure control valve 7a.
They are expressed using the same numerals and subscripted by b. ) has a cylinder 12a connected to a pressure adjustment spring 11a that changes the set value of the main valve portion 10a. This cylinder 1
2a is a rod 1 that comes into contact with the pressure adjustment spring 11a;
A pilot circuit 9a is connected to a head side pressure chamber 15a of the piston 14a. (A pilot circuit 9b is connected to the head side pressure chamber 15b of the cylinder 12b of the pressure control valve 7b.) This pressure control valve 7a is operated by the rod 13a pressing the pressure adjustment spring 11a by the pilot oil pressure of the pilot circuit. , the set point is increased.

In the conventional pressure control valve 7a having the above structure, when the pilot hydraulic pressure acts on the pilot circuit 9a, the directional control valve 2 switches to the switching position 2b, and the pilot hydraulic pressure acting on the head side pressure chamber of the cylinder 12a causes the spring 11a to Main valve part 10 is pressed
Increase the set value of a. Therefore, the hydraulic motor 4 is supplied with the pressure oil of the hydraulic pump 1, and the arrow A
The swivel base 5 is driven in one direction.

Furthermore, when pilot oil pressure acts on the pilot circuit 9b, the set value of the pressure control valve 7b increases and the directional switching valve 2 switches to the switching position 2c.
The hydraulic motor 4 drives the swivel base 5 in the direction of arrow A2. After the hydraulic motor 4 drives the swivel base 5 in the direction of the arrow A1, when the pilot oil pressure of the pilot circuit 9a is lowered, the directional control valve 2 is activated by the spring 2.
g, the main circuits 6a and 6b are closed, but the hydraulic motor 4 is
It is driven in the direction of arrow A1 by the inertia force due to the load of the swivel base 5, and pumps the oil in the main circuit 6a to the main circuit 6b. This pressure oil flows into the main circuit 6a via the pressure control valve 7b. At this time, the oil pressure in the main circuit 6b is a set value due to the pressing force of the spring 11b of the pressure control valve 7b, and a braking force based on the set value of the pressure control valve 7b acts on the hydraulic motor 4. (Note that when the hydraulic motor 4 is stopped from being driven in the direction of arrow A2, the spring 11 of the pressure control valve 7a
A braking force of a set value according to a is applied. ) If the pressing force of the pressure regulating spring of the pressure control valve having the above-mentioned configuration is increased, the braking force will be increased, but high pressure will be applied when the hydraulic motor is started. Therefore, the pressing force of the pressure adjustment spring is set weakly, and when the hydraulic motor is started, a means is taken to increase the set value of the pressure control valve in accordance with the pilot oil pressure acting on the cylinder. As a result, the braking force applied to the hydraulic motor becomes weak when the directional control valve is in the neutral position, so a mechanical brake device is provided on the hydraulic motor, and this mechanical brake device locks the swivel base when the directional control valve is in the neutral position. . Therefore, when inserting this circuit, it is necessary to perform two operations: releasing the brake of the mechanical brake device and applying pilot oil pressure to the pilot circuit. This has the disadvantage that the operation becomes complicated.

The technical problem of the present invention is to set a high set value when no pilot oil pressure is applied, lower this set value to a low pressure set value using the pilot oil pressure, and then raise it to a value corresponding to the pilot oil pressure. It is.

In order to solve this technical problem, the present invention provides a pressure control valve having a cylinder equipped with a piston to which a rod is fixed, which contacts a pressure adjustment spring that changes the set value of the pressure control valve. A rod-side pressure chamber to which the pilot circuit is connected is provided, and a second piston is provided on the head side that comes into contact with the piston of the cylinder and is pressed by a spring with a stronger pressing force than the pressure adjustment spring. A head side pressure chamber is formed between the head side pressure chamber and the rod side pressure chamber, and the head side pressure chamber and the rod side pressure chamber are connected by a passage provided with a restriction.
Use technical means.

This technical means is such that when the pilot oil pressure does not act on the rod side pressure chamber, the set value of the pressure control valve is set to a value corresponding to the pressing force of the spring that presses the second piston, and the pilot oil pressure causes the second piston to move. After releasing the pressing force of the spring that presses the piston, the pressure adjusting spring is pressed by the pressing force of the piston. Therefore, even if the set value of the pressure control valve is set to a high pressure when the pilot oil pressure does not act, when the pilot oil pressure acts, the set value can be reset to a value corresponding to the pilot oil pressure after the set value is released. Therefore, if this pressure control valve is used in the drive circuit of a hydraulic motor, a mechanical brake device for the hydraulic motor can be omitted, and its operation can be made as simple as applying pilot hydraulic pressure to the pilot circuit. can.

The present invention having the above configuration has the following unique effects.

As another technical means for solving the technical problems of the present invention, as shown in FIG.
A pilot circuit 20 equipped with an ACC is provided, and switching valves 21a, 21b are provided between the pilot circuit 20 and each of the pressure control valves 7a, 7b, which are switched by the pilot oil pressure of the pilot circuits 9a, 9b. The switching valves 21a, 21b switch between the pilot circuit 20 and the pressure control valves 7a, 7b when no pilot oil pressure acts on the pilot circuits 9a, 9b.
Head side pressure chamber 15 of cylinder 12a, 12b
Switching positions 21c and 21 connecting a and 15b
c' and the pilot oil pressure of the pilot circuits 9a, 9b act, the cylinders 12a,
12b to the pilot circuits 9a, 9b.

According to this means, the pilot circuits 9a, 9b
When the pilot oil pressure does not act on the pilot circuits 9a and 9b, the set values of the pressure control valves 7a and 7b can be set according to the oil pressure of the pilot circuit 20, and when the pilot oil pressure of the pilot circuits 9a and 9b acts,
Head side pressure chambers 15 of cylinders 12a, 12b of switching valves 21a, 21b and pressure control valves 7a, 7b
After the pressure oils a and 15b are discharged into the tank, the pressure is controlled by applying the pilot oil pressure of the pilot circuits 9a and 9b to the head side pressure chambers 15a and 15b of the cylinders 12a and 12b of the pressure control valves 7a and 7b. After the set values of the valves 7a, 7b are lowered to a low value, they can be controlled to a value corresponding to the pilot oil pressure of the pilot circuits 9a, 9b.

With this means, the set value of the pressure control valve cannot be maintained due to the pressure drop in the accumulator. In particular, when this means is used in the drive circuit of the swivel table and the pressure in the accumulator falls, the swivel table is There is no longer any parking brake force to lock the parking brake.
There is a danger that the swivel base will rotate due to the load.

In the present invention, the set value of the pressure control valve is maintained by the pressing force of the spring when no hydraulic pressure is applied to the pilot circuit, so the set value of the pressure control valve is maintained even when no pilot hydraulic pressure is applied to the pilot circuit. Reliable braking force (parking brake force) because it can be maintained at a predetermined set value
It has the effect of being able to obtain.

Hereinafter, a description will be given with reference to FIG. 3, which shows an embodiment in which the present invention is implemented in a pilot type pressure control valve.

FIG. 3 shows the same hydraulic circuit for driving the swivel base as the circuit shown in FIG. This third
In the figure, the pressure control valve 7a' includes a main valve part 10a' that includes a main valve 25a' that responds to the opening and closing of the main pilot valve 26a', a pressure adjustment spring 27a' that presses the pilot valve 26a', and a pressure regulating spring 27a' that presses the pilot valve 26a'. It is composed of a cylinder 12a' that applies a pressing force to the adjustment spring 27a'.

The cylinder 12a' has a piston 29 to which a rod 28a' connected to a pressure adjustment spring 27a' is fixed.
A' and a second piston 31a' that abuts this piston 29a' are slidably fitted into the inner hole 30a'. A spring 32a' is provided behind the second piston 31a'. A head side pressure chamber 33a' is formed between the second piston 31a' and the piston 29a'.
They are connected by a passage 36a' with an a' throttle 35a'. The pressure chamber 34a' on the rod side is connected to the pilot circuit 9a. Note that the pressure control valve 7b' has the same configuration as the pressure control valve 7a', so a description thereof will be omitted.

Next, the operation of this embodiment will be described.

When pilot hydraulic pressure does not act on either of the pilot circuits 9a, 9b, the pressure control valves 7a', 7
The set value of b' means that the pressing force of the springs 32a' and 32b' is applied to the pressure adjustment springs 27a' and 27b', and the second piston 31
Since it acts via a', 31b' and pistons 29a', 29b', the value corresponds to the pressing force of springs 32a', 32b'. Therefore, these springs 32a', 32
By setting the pressing force of b' to the value necessary for the parking brake force of the swivel base 5, the main circuit 6a,
Since 6b can hold high hydraulic pressure,
It acts as a braking force when the hydraulic motor 4 is driven by an external force acting on the swivel base 5 (wind force or an external force on the swivel base 5 that is applied when a construction machine is stopped on a slope).

When the pilot oil pressure is applied to the pilot circuit 9a, the pilot oil pressure acts on the pilot portion 2d of the directional control valve 2 and also on the pressure control valve 7.
It acts on the rod side pressure chamber 34a' of a'.

When pilot oil pressure acts on the pilot portion 2d, the directional control valve 2 is switched to the switching position 2b. Therefore, the main circuit 6a is connected to the hydraulic pump 1, and the main circuit 6b is connected to the tank. Therefore, pressure oil discharged from the hydraulic pump 1 is supplied to the hydraulic motor 4 via the main circuit 6a, and oil from the hydraulic motor 4 flows out from the main circuit 6b to the tank.

The pressure control valve 7a' allows the pilot hydraulic pressure acting on the rod side pressure chamber 34a' to pass through the passage 36a' and the throttle 35.
It acts on the head side pressure chamber 33a' via a'. Therefore, when the pressing force of the pilot oil pressure exceeds the pressing force of the spring 32a', the second piston 31a' moves to the right and separates from the piston 29a'. At this time, the force acting on the piston 29a' is the pressing force of the pressure adjustment spring 27a' and the pressing force of the pilot oil pressure acting on the rod side pressure chamber 34a' acting in the right direction, and acting on the head side pressure chamber 33a'. The pressing force from the pilot hydraulic pressure acts to the left. Since the pressing force acting in the left direction is the value obtained by dividing the pressing force of the spring 32a' by the pressure receiving area of the head side pressure chamber 33a', the pilot oil pressure of the head side pressure chamber 33a' is equal to the pressure of the rod side pressure chamber 34a. The pressure will be lower than the pilot oil pressure of '. Therefore, the piston 29a' and the second piston 31a' are activated almost simultaneously.
Move to the right until the right end of a' touches the main body. As the piston 29a' and the second piston 31a' move to the right, the pressing force of the pressure adjustment spring 27a' decreases, so that the set value of the pressure control valve 7a' is set so that the second piston 31a' is at its maximum. The set value (lowest set value) corresponds to the pressing force of the pressure adjustment spring 27a' when the right end is reached. and second piston 31
When a' comes into contact with the main body, the pilot oil pressure in the head side pressure chamber 33a' increases due to the pilot pressure oil supplied from the rod side pressure chamber 34a', and the piston 2
9b' moves to the right under the following conditions.

Now, if the parts and pressure values of the pressure control valve 7a' are set as follows, the pressure receiving area _A1 of the rod side pressure chamber 34a', the pilot oil pressure _P1 , the pressure receiving area _A2 of the head side pressure chamber 33a', and the pilot pressure Hydraulic pressure P ₂ Pressure receiving area A of rod 28a' ₃ Minimum pressing force F of pressure adjustment spring 27a' ₁ Pressing force F in the right direction acting on piston 29a' ₂ Pressing force F acting in the left direction acting on piston 29a' ₃ When the piston 29a' and the piston 31a' are at the rightmost end, F ₂ =F ₃ (1).

In order for the piston 29a' to start moving leftward, F ₂ <F ₃ (2).

Here, F ₂ = F ₁ + P ₁・A ₁ …(3) F ₃ = P ₂・A ₂ …(4) A ₁ = A ₂ −A ₃ …(5) Therefore, from equation (1), When F ₁ + P ₁・A ₁ = P ₂・A ₂ ,
When the piston 29a' is stopped and F ₁ +P ₁ ·A ₁ <P ₂ ·A ₂ (6), the piston 29a' starts moving to the left. And the values of A ₁ , A ₂ , F ₁ are the pressure control valve 7
Since the value is determined by a′, the piston 29
From equations (5) and (6), a' starts to move to the left when the pilot oil pressure P ₁ P ₂ satisfies F ₁ + A ₂ (P ₁ − P ₂ ) < P ₁ A ₃ ...(7) . That is, P ₁ ≒
P ₂ , the piston 29a' presses the pressure adjustment spring 27a' with a pressing force resulting from the product of the pressure receiving area of the rod 28a' and the pilot oil pressure P ₁ , and the pressing force of the pressure adjustment spring 27a' becomes F. Increasing from ₁ to F ₁ ′, Eq.
When both sides of (7) are equal, the piston 29a' becomes
Stop at that position. Further, the time it takes for the piston 29a' to stop from the rightmost end is approximately determined by the volume of the head side pressure chamber 33a' and the opening area of the throttle 35a'.

As described above, the pressure control valve 7a' is once lowered to the lowest set value by the pilot oil pressure acting on the pilot oil pressure, and then raised to the set value corresponding to the pilot oil pressure. Therefore, since the oil pressure in the main circuit 6a is controlled by the operation of the pressure control valve 7a', sudden oil pressure is not applied to the hydraulic motor 4.
Therefore, the hydraulic motor 4 is started smoothly.

The case where the pilot oil pressure is applied to the pilot circuit 9a has been described above, but when the pilot oil pressure is applied to the pilot circuit 9b, the pressure control valve 7b' acts in the same manner as the pressure control valve 7a', so a description thereof will be omitted. .

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram using a conventional pressure control valve, Fig. 2 is a partial hydraulic circuit diagram showing another example of Fig. 1, and Fig. 3 is a pressure control valve according to an embodiment of the present invention. It is a hydraulic circuit diagram using. 1... Hydraulic pump, 2... Directional switching valve, 4... Hydraulic motor, 7a', 7b'... Pressure control valve, 10a', 10
b'...Main valve part, 12a', 12b'...Cylinder, 13
a, 13b...rod, 14a, 14b...piston, 27a', 27b'...pressure adjustment spring, 29a', 2
9b'...Piston, 31a', 31b'...Second piston, 32a', 32b'...Spring, 33a', 33b'...Head side pressure chamber, 34a', 34b'...Rod side pressure chamber, 35a', 35b' ...Aperture, 36a', 36b'...Passage.

Claims (1)

[Claims] 1. In a pressure control valve having a cylinder equipped with a piston to which a rod is fixed, which contacts a pressure adjustment spring that changes the set value of the pressure control valve, a rod side pressure chamber to which a pilot circuit is connected is provided on the rod side of the cylinder. A second piston is provided on the head side, which abuts the piston of the cylinder and is pressed by a spring having a stronger pressing force than the pressure adjustment spring, and a head side pressure chamber is formed between the second piston and the piston. , a pressure control valve in which the head side pressure chamber and the rod side pressure chamber are connected by a passage provided with a restriction.